Chapter One
Linear Partial Differential
Equations of Mixed Type
Consider the equation
(1.1) [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII]
where the coefficients are supposed to be smooth enough:
k, a [element of] [ITLITL.sup.3] (
[bar.G]);
[alpha], c [element of] [ITLITL.sup.2](
[bar.G]), and
(1.2)
a(
x, y) [greater than or equal to] [delta] > 0
in the rectangle
[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII]
Formulation of boundary value problems for Equation (1.1) depends on the signs
of the coefficient
k(
x, y) at
x = 0 and
x =
l. In a
basic problem we
suppose that the type of equation is elliptic on the front and exit sides
x = 0,
x =
1 of the
rectangle
G, and prescribe boundary conditions on the whole perimeter of
G. Moreover, we assume
that the inequality 2[alpha] ±
[k.sub.x] [greater than or equal to] [delta] > 0 with ...
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